11.6.7 Grading-up

This is the method used to change a population of animals quickly from one breed to another. Sires of the newly desired breed are continually backcrossed to the females from the previous generation. After three generations the F₃ animals contain already for 87,5 % the genes of the desired breed and after four or five generations the population fully resembles the desired parental breed. Such a process took place in Western Europe in the 70-ties of the past century when local Black and White cattle populations were graded-up with Holstein Friesian sires from North America creating the present European Holstein Friesian cattle breed.

Percentage of Dutch Friesian and Holstein Friesian genes in Dutch Black and White cows per year of birth. (Source: CRV)

The figure above shows the rapid replacement by upgrading of the Dutch Friesian by the Holstein Friesians from North America. The downside of grading-up is that original breed may disappear. For instance, the Dutch Friesian is a small population nowadays